The present invention is directed to handlebars and, more particularly, to handlebars with an adjustable dampening mechanism for motorcycles, bicycles, all terrain vehicles, and personal watercrafts.
Handlebars for motorcycles generally comprise a single length of low carbon alloy steel tube appropriately bent to provide a central region, bent regions, and respective handgrip regions, the former being clamped at one or two positions to form a connection to the main cycle frame via an intermediate top yoke or stem. To reduce weight, aftermarket handlebars are typically formed from aluminum. For additional strength, it has been conventional to provide a crossbar spanning the central region of the aluminum tube. Alternatively, the handlebar may be strengthened by providing an aluminum tube with a greater external diameter at the central region, wherein the diameter of the aluminum tube is gradually reduced towards the distal ends.
U.S. Pat. No. 4,635,499 discloses a conventional handlebar 10 of the first type. This type of handlebar 10 is commonly used for offroad motorcycles, all terrain vehicles and personal watercrafts. Referring to FIG. 1, the handlebar 10 has a central region 12, two bent regions 14, 16, and two handgrip regions 18, 20. The diameter of the handlebar 10 is uniform throughout the entire lengthwise dimension. In general, the preferred diameter of conventional handlebars is xe2x85x9e inch because this provides the handgrip regions 18, 20 with the proper amount of thickness so that a handgrip with a thickness of approximately xe2x85x9 to xc2xc inch can be fitted over a portion of each handgrip region 18, 20. Although a xe2x85x9e inch diameter tubing 22 is ideal for facilitating a properly sized handgrip for the rider, the tubing 22 does not have sufficient strength to withstand the impact of heavy loads. As such, a crossbar 24 is used to reinforce the tubing 22 and to prevent the tubing 22 from buckling. The crossbar 24 is attached between the two bent regions 14, 16 and is oriented generally parallel to the central region 12. When the crossbar 24 is used, a permanent compression set occurs in the bent regions 14, 16 in the event of an impact. Furthermore, the crossbar 24 provides no added benefit when steering the vehicle because the crossbar 24 reinforces the handlebar 10 in only the vertical direction while providing no reinforcement in the horizontal direction. Another problem with the crossbar 24 is that a permanent compression set may occur in the event of an impact because the attachment points 26, 28 of the crossbar 24 at the bent regions 14, 16 act as a stress concentration site. In addition, the crossbar 24 constrains any movement of the tubing 22 that would soften shock loads to the handgrip regions 18, 20. The crossbar 24 may further be a safety hazard. In particular, the rider may impact the crossbar during a crash.
In order to resolve some of the problems associated with crossbars, U.S. Pat. No. 5,257,552 discloses an integrally formed unitary hollow tubular handlebar 50 of the latter type wherein the wall thickness is greatest and constant in the central region 52, smallest and constant at the handgrip regions 54, 56, and tapering in the bent regions 58, 60 as shown in FIG. 2. This improved handlebar 50 eliminates the need for a crossbar by increasing the diameter and sidewall thickness of the central region 52 of the handlebar 50, while the reduction in diameter along the bent regions 58, 60 and handgrip regions 54, 56 allows the use of standard handgrips. Without the crossbar, the handlebars 50 has a longer unsupported span, thereby providing more cushioning strength and greater steering control. However, the problem with such a configuration is that a custom triple clamp assembly must be used to secure the handlebar 10 to the main frame of the vehicle because the diameter of the central region 52 is greater than the standardized xe2x85x9e inch diameter. As a result, the available selection of triple clamp assemblies is relatively limited and custom units, which are generally costly, may be required. Furthermore, it is substantially more costly to fabricate tapered handlebars than handlebars with uniform tubes.
U.S. Pat. No. 6,182,528 discloses another handlebar configuration which eliminates the need of a crossbar by having a unitary handlebar 100 comprising an inner tubular member 102 of constant diameter and constant wall thickness and an outer tubular sleeve 104 surrounding the inner tubular member 102 as shown in FIG. 3. Both the inner tubular member 102 and the outer tubular sleeve 104 have a central region 106, bent regions 108, 110, and handgrip regions 112, 114. The handgrip regions 112, 114 of the inner tubular member 102 extend beyond the handgrip regions 112, 114 of the outer tubular sleeve 104. The two-layer configuration allows the use of two different materials to provide a stronger, but more notch sensitive material for the inner tubular member 102 and a more ductile but less notch sensitive material with greater fatigue resistant properties for the outer tubular sleeve 104. This configuration is advantageous in minimizing stress and impact damage at the locations where the handlebar 100 is clamped to the triple clamp assembly. In the manufacturing process, the inner tubular member 102 and the outer tubular sleeve 104 are formed separately from metal tubes. The thickness of the outer tubular sleeve 104 is reduced prior to insertion of the inner tubular member 102. Thereafter, the outer tubular sleeve 104 and inner tubular member 102 are shaped together by bending in a conventional manner. Although the outer tubular sleeve 104 comprises a xe2x85x9e outer diameter which is compatible with standard triple clamp assemblies, the fabrication costs are relatively high due to the two-layer construction.
In view of the above, it is apparent that there is a need to provide a handlebar which is capable of withstanding large impact loads while being sufficiently flexible to dampen some of the impact loads. However, the preferred dampening characteristics of the handlebar may depend on the particular riding application (i.e. moto-cross, super cross, desert riding, etc.), physical characteristics of the rider (i.e. size, weight, strength, etc.), suspension system of the vehicle (i.e. spring rate of the fork tubes, xxx, etc.), and the personal preference of the rider. This is particularly important for racing purposes where a slight improvement in the performance of the vehicle provides the rider with a competitive advantage. An operator may incur substantial costs to meet these requirements, wherein a number of prototype handlebars may be needed to first determine the appropriate handlebar configuration for a particular rider and track. Since a rider usually operates the vehicle at several tracks, an inventory of handlebars tailored for each or at least some of the tracks may be needed. In addition to the development and inventory costs, preparation of the vehicle for a particular track may include removal and installation of the handlebar. Thus, there is a need to provide a handlebar which is adaptable to various track and rider conditions. There is also a need to provide a handlebar which is lightweight, durable, easy to manufacture, compatible with existing vehicles, and relatively inexpensive.
In accordance with the present invention, a handlebar is provided with a titanium tubing capable of absorbing impact loads to reduce rider fatigue and enhance control of a vehicle. In particular, the handlebar is configured with a relatively long unsupported span which allows the tubing to react more readily to impact loads by flexing. The handlebar includes a central region having a first end and a second end, a first bent region extending from the first end of the central region, a second bent region extending from the second end of the central region, a first handgrip region extending from a distal end of the first bent region, and a second handgrip region extending from a distal end of the second bent region. Bent portions adjoin each of the regions. The handlebar is formed by extruding the tubing, cutting the tubing to the desired length, and bending the tubing in the extruded state.
The handlebar further includes an adjustable dampening mechanism which allows an operator to vary the stiffness of the handlebar. The adjustable dampening mechanism includes a rod disposed within the tubing, wherein the rod contacts the internal wall of the tubing at the bent portions. The bending resistance of the rod at the bent portions increases the stiffness of the handlebar. Stiffness of the handlebar can be increased or decreased by respectively increasing or decreasing rod tension.
Other aspects, features and techniques of the invention will become apparent to one skilled in the relevant art in view of the following detailed description of the invention.